Glossary

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Force applied to a pipeline or drill string to propel it through the ground.

Thrust Jacking Method

Method in which a pipe is jacked through the ground without mechanical excavation of material from the front of the pipeline.

Thrust Pit

Working shaft at the beginning of the jacked section of pipeline in which the specialist equipment is installed, and from which jacking operations are carried out.

Thrust Ring

A steel ring that is placed against the cross sectional area of the pipe to ensure that the jacking forces are spread around the circumference of the pipe.

Thrust Wall

A wall at the rear of the thrust pit designed to spread the reaction loads to the ground behind the thrust pit.

Thrust/Pullback

Measured in pounds or similar measurements of force; along with torque and pump capacity, one of three measurements typically used to describe and classify drill rigs and their suitability to successfully perform an installation.

Torque

Measured in Foot-pounds or similar measurements of rotational force; along with thrust/pullback and pump capacity, one of three measurements typically used to describe and classify drill rigs and their suitability to successfully perform an installation.

Tracking

System for locating and recording progression of a horizontial drilling installation by monitoring an electromanetic signal transmitted from a sonde mounted at the drill head to a receiver (locator) at the surface, or by wireline or wireless non-walkover systems.

Trailing Interjack Pipe

The recessed pipe immediately behind the interjack station which slides into the rear of the shield.

A machine that excavates a tunnel by drilling out the face to full size in one operation. It may be controlled from within the shield or remotely.

Tunneling

A construction method of excavating an opening beneath the ground without continuous disturbance of the ground surface and of large enough diameter to allow individuals access and erection of a ground support system at the location of material excavation.